(192f) Pressurized Oxy-Fuel Combustion in Fluidized Bed: 3D CFD Simulation with Experiment

Abstract

For reducing
the global greenhouse gas emissions and slowing global warming from the process
of industrialization, carbon capture and storage (CCS) technologies have been supposed
to reduce carbon dioxide emission apply from the power plants and fossil
industries. Oxy-fuel combustion technology has been considered as a promising
means to achieve the objective of effective CO₂ capture with
commercial potential. The fluidized bed with oxy-fuel combustion technology can
fire coal and low quality fuels like solid wastes and biomass with high
efficiency and lower pollutants emissions. However, the net efficiency will fall
by more than 10% primarily caused by the high energy consumption of air
separation unit (ASU) and the compression purification unit (CPU) and the
pressure mismatch among the ASU, furnace and CPU. Pressurized oxy-fuel
combustion (POFC) technology as a new generation of oxy-fuel combustion
technology is a perspective application in industrial process due to its higher
net efficiency and combustion efficiency than ordinary oxy-fuel combustion.

Understanding
the detail gas-solid flow and combustion characteristics is of paramount
importance to the design, operation and optimization of oxy-fuel FB reactors. In this work, a 3D Eulerian-Lagrangian
model including particle flows and chemical reactions was developed to simulate the pressurized oxy¨Cfuel combustion
process in FB (Fig. 1) based on the Multi-Phase Particle-In-Cell (MP-PIC)
scheme, and the particle size distribution was particularly taken into account. As shown Fig. 2, this model successfully predicts critical
parameters by comparing with the experimental data from a pilot-scale 15 kW_th pressurized fluidized bed. On this foundation, some detailed combustion characteristics and
full-physics picture including particle flow behavior that are hardly measured
by experiment were simulated. The simulated results show that the intensity of
particle motion and expansion degree of bed was gradually decreased with an increase in pressure under same gas flow
rate. The higher operating pressure led to higher particle concentrations in
the furnace and caused the variation of flow pattern. the temperature of solid
phase region gradually increased with pressure and inlet O₂
concentration increased. In addition, the elevated pressure and inlet O₂
concentration can help to reduce the emission of CO and NO_x. In
addition, the size and size distribution of coal in FB were also study in this
work with different operating pressure and inlet oxygen concentration. This
work can be expected to improve and optimize the scale-up pressurized oxy-fuel
FB system for industrial application in future research.

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1. Three-dimensional CFB model simplified from
the 15 kW_th pilot-scale pressurized fluidized bed

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                           (b)

Fig. 2. Comparison of the predicted
results and the experimental data under different conditions

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